Spindle device

Abstract

This spindle device comprises: a housing (2); a rolling bearing (21) that rotatably supports a rotating shaft (3) relative to the housing (2); a first outer ring spacer (41) that is disposed axially forward of the rolling bearing (21), which is exposed to a liquid atmosphere, and that positions the outer ring of the rolling bearing (21) in the axial direction relative to the housing (2); a first inner ring spacer (45) that is disposed radially inward of the first outer ring spacer (41) and that positions the inner ring of the rolling bearing (21) in the axial direction relative to the rotating shaft (3); grease reservoir recesses (42, 46) provided on an inner peripheral surface (41c) of the first outer ring spacer (41) and an outer peripheral surface (45c) of the first inner ring spacer (45), which face each other in proximity to each other; a surface treatment layer (50) having a water-repellent and oil-repellent effect applied to the surfaces of the first outer ring spacer (41) and the first inner ring spacer (45); and grease (60) filled in the grease reservoir recesses (42, 46).

Description

Spindle device

[0001] The present invention relates to a spindle device, and more particularly to an improvement in a spindle device that prevents liquid from entering from the outside and improves waterproofing.

[0002] The rotating shaft of the spindle in a machine tool's spindle unit rotates at high speeds while cutting or grinding. It is necessary to spray a large amount of liquid forcefully onto the workpiece for lubrication purposes (e.g., to improve cutting characteristics (sharpness), reduce wear on the tool cutting edge, and extend tool life) and cooling purposes (e.g., to improve machining accuracy by suppressing temperature rise in the tool and workpiece, to prevent welding due to heat generated at the workpiece, to improve machining efficiency, and to prevent deterioration of the workpiece's surface quality and quality due to heat (sparks, etc.)).

[0003] As a result, since the machining area is close to the spindle, a large amount of liquid also gets on the front of the spindle. If this liquid gets inside the bearing, it can cause problems with lubrication and seizure, so waterproofing is important.

[0004] For this reason, spindle units have traditionally used methods such as sealed grease lubrication, grease replenishment lubrication, oil and air lubrication, and oil mist lubrication. In particular, with sealed grease lubrication and grease replenishment lubrication, compared to oil and air lubrication and oil mist lubrication, the internal pressure is lower because air is not pumped into the spindle, resulting in inferior waterproof performance, making waterproof performance important. In contrast, with oil and air lubrication and oil mist lubrication, air is pumped inside, which makes the internal pressure of the spindle greater than the external pressure (atmospheric pressure), creating an air flow from inside the spindle to the outside, making it difficult for liquids to penetrate from outside.

[0005] 10 , in a conventional spindle unit 101, the rotating shaft 103 is rotatably supported relative to the housing 102 by a front bearing unit 120 arranged axially forward of the rotating shaft 103 and a rear bearing unit (not shown) arranged axially rearward of the rotating shaft 103. The front bearing unit 120 is equipped with four rolling bearings 121 assembled back-to-back with an outer ring spacer 123 and an inner ring spacer 125 sandwiched therebetween.

[0006] The four rolling bearings 121 have their outer rings fixed to the housing 102 by the front cover 113, and their inner rings fixed to the rotating shaft 103 with a predetermined preload applied by nuts 127. An inner ring spacer 115 fitted onto the rotating shaft 103 is interposed between the rotating shaft 103 and the inner rings.

[0007] A cover 111 is placed in front of the rotating shaft 103, and the gap between the inner ring spacer 115 attached to the rotating shaft 103 and the front cover 113 inside the cover 111 is made into a labyrinth structure to prevent the intrusion of liquids from outside. However, if a large amount of liquid is sprayed onto the front surface of the spindle, the liquid may pass through the labyrinth and enter the inside of the bearing, possibly causing damage to the bearing.

[0008] Therefore, Patent Document 1 describes a bearing waterproofing mechanism that can extend the life of the bearing by forming a labyrinth gap between a housing and a member attached to the rotating shaft and waterproofing the surfaces of both members that form the labyrinth gap by providing a water-repellent coating. Also, Patent Document 2 describes a waterproof structure for an output shaft that provides a grease reservoir at the output shaft abutment part of a rubber seal that abuts against the rotating sliding part of the output shaft, thereby reducing the effect of part precision on the seal of the sliding part.

[0009] Japanese Patent Publication No. 2002-327764 Japanese Patent Publication No. 2006-187076

[0010] However, with the conventional waterproof structures described above, it is difficult to adequately prevent liquid from penetrating into the bearing when a large amount of liquid is sprayed onto it, such as in the spindle device of a machine tool, and further improvements in waterproofing are desired.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a spindle device that can prevent liquid from entering from the outside and improve waterproofing.

[0012] The above object of the present invention is achieved by the following configuration (1): (1) A spindle device comprising: a housing, a rolling bearing that rotatably supports a rotating shaft relative to the housing, a first outer ring spacer that is arranged axially forward of the rolling bearing that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing axially relative to the housing, a first inner ring spacer that is arranged radially inward of the first outer ring spacer and that positions the inner ring of the rolling bearing axially relative to the rotating shaft, grease reservoir recesses provided on at least one of the inner peripheral surface of the first outer ring spacer and the outer peripheral surface of the first inner ring spacer that are closely opposed to each other, surface treatment layers that have water and oil repellency and are applied to the surfaces of the first outer ring spacer and the first inner ring spacer, and grease filled in the grease reservoir recesses.

[0013] According to the spindle device of the present invention, it is possible to prevent the intrusion of liquid from the outside and improve waterproofing.

[0014] FIG. 1 is a longitudinal sectional view of a spindle unit according to a first embodiment of the present invention. FIG. 2 is an enlarged sectional view of a front bearing device arranged axially forward of the spindle unit shown in FIG. 1. FIG. 3 is an enlarged sectional view of a main portion of the front bearing device shown in FIG. 2. FIG. 4 is an enlarged sectional view of a main portion of the front bearing device in a spindle unit according to a second embodiment of the present invention. FIG. 5 is an enlarged sectional view of a main portion of the front bearing device in a spindle unit according to a third embodiment of the present invention. FIG. 6 is an enlarged sectional view of a main portion of the front bearing device in a spindle unit according to a fourth embodiment of the present invention. FIG. 7 is an enlarged sectional view of a main portion of the front bearing device in a spindle unit according to a fifth embodiment of the present invention. FIG. 8 is an enlarged sectional view of a main portion of the front bearing device in a spindle unit according to a sixth embodiment of the present invention. FIG. 9 is an enlarged sectional view of a main portion of the front bearing device in a spindle unit according to a seventh embodiment of the present invention. FIG. 10 is an enlarged sectional view of a front bearing device in a conventional spindle unit.

[0015] The spindle devices according to the respective embodiments of the present invention will be described in detail below with reference to the drawings. Note that the spindle devices of the respective embodiments will be described as being applied to spindle devices for machine tool spindles, but it goes without saying that they can also be applied to spindle devices for high-speed motors, or spindle devices for rotating machines that rotate at high speeds, such as centrifuges and turbo refrigerators.

[0016] 1 is a longitudinal sectional view of a spindle unit 1 according to a first embodiment of the present invention. In the spindle unit 1 according to the first embodiment, as shown in FIG. 1, a rotary shaft 3 is rotatably supported with respect to a housing 2 by a front bearing device 20 arranged axially forward of the rotary shaft 3 and a rear bearing device 30 arranged axially rearward of the rotary shaft 3.

[0017] The rotary shaft 3 is configured in a hollow cylindrical shape, and a draw bar 5 is provided inside the cylinder, which is biased by a disc spring 4 and is slidable inside the cylinder. A chuck portion 6 is provided at the tip of the draw bar 5 to hold and release a tool attached to the rotary shaft 3.

[0018] The front bearing device 20 has four rolling bearings 21 assembled back-to-back with an outer ring spacer 23 and an inner ring spacer 25 sandwiched therebetween, and the rear bearing device 30 has one rolling bearing 31. Of course, the number and combination form of the plurality of rolling bearings 21 to be assembled are not limited to this.

[0019] The rear bearing device 30 is a bearing device that includes a rolling bearing 31, which is a cylindrical roller bearing that supports the rotating shaft 3 so that it can rotate freely relative to the housing 2, an outer ring holder 17, which is an outer ring positioning member that is fitted inside the housing 2 and positions the outer ring of the rolling bearing 31 in the axial direction, and an inner ring holder 19, which is an inner ring positioning member that is fitted outside the rotating shaft 3 and positions the inner ring of the rolling bearing 31 in the axial direction.

[0020] Fig. 2 is an enlarged sectional view of a front bearing device 20 arranged axially forward of the spindle unit 1 shown in Fig. 1. Fig. 3 is an enlarged sectional view of a main portion of the front bearing device 20 shown in Fig. 2. The front bearing device 20 according to the first embodiment is a bearing device including a housing 2 and rolling bearings 21, which are four angular contact ball bearings assembled back to back, for rotatably supporting the rotating shaft 3 relative to the housing 2, as shown in Fig. 2.

[0021] The front bearing device 20 is disposed axially forward (to the left in FIG. 2 ) of the rolling bearing 21, which is exposed to a liquid atmosphere, and comprises a first outer ring spacer 41 that axially positions the outer ring of the rolling bearing 21 relative to the housing 2, a second outer ring spacer 13 interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41, and an outer ring holder 31. A cover 11 that covers the front bearing device 20 and fixes the outer ring holder 31 to the housing 2 is attached to the front side of the housing 2.

[0022] The cylindrical first outer ring spacer 41 fitted inside the housing 2 has its outer surface liquid-tightly sealed against the housing 2 by an O-ring 51 arranged on the inner surface of the housing 2.

[0023] A discharge port 14 that penetrates radially is formed in a cylindrical second outer ring spacer 13 that is fitted into the housing 2. When the second outer ring spacer 13 is fitted into the housing 2, it is assembled so that the discharge port 14 communicates with a lubricant discharge port 35 that is provided vertically below the housing 2.

[0024] An outlet port 33 that penetrates radially is formed in the outer ring retainer 31 that is fixed to the open end of the housing 2. When the outer ring retainer 31 is fixed to the housing 2, it is assembled so that the outlet port 33 is positioned vertically downward.

[0025] Furthermore, the front bearing device 20 includes a first inner ring spacer 45 that is arranged radially inward of the first outer ring spacer 41 and that positions the inner ring of the rolling bearing 21 in the axial direction with respect to the rotating shaft 3, and a second inner ring spacer 15 that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45. The front bearing device 20 also includes a nut 27 that is fixed to the rotating shaft 3 with a predetermined preload applied to the inner ring of the bearing between it and the shoulder 3 a of the rotating shaft 3.

[0026] The cylindrical first inner ring spacer 45 that is fitted onto the rotating shaft 3 has its inner surface liquid-tightly sealed against the rotating shaft 3 by an O-ring 53 arranged on the outer surface of the rotating shaft 3.

[0027] 3, when disposed axially forward of the rolling bearing 21, the inner circumferential surface 41c of the first outer ring spacer 41 and the outer circumferential surface 45c of the first inner ring spacer 45, which are closely opposed to each other, have a cylindrical shape extending axially forward. Furthermore, the inner circumferential surface 41c of the first outer ring spacer 41 and the outer circumferential surface 45c of the first inner ring spacer 45 are respectively provided with grease reservoir recesses 42, 46. The grease reservoir recesses 42, 46 are circumferential grooves with rectangular cross sections, and are each filled with grease 60.

[0028] Furthermore, a surface treatment layer 50 (shown by cross-hatching in FIG. 3) having water- and oil-repellent properties is applied to the surfaces of the first outer ring spacer 41 and the first inner ring spacer 45. The surface treatment layer 50 is applied to the surfaces of the first outer ring spacer 41 and the first inner ring spacer 45, for example, by coating them with a fluororesin or silicone resin, or by coating them with an oil-repellent agent made of a fluorine-based compound.

[0029] It is desirable that the surface treatment layer 50 be applied to at least the front and rear end faces (both axial end faces) 41a, 41b and inner peripheral surface 41c of the first outer ring spacer 41, and the front and rear end faces 45a, 45b and outer peripheral surface 45c of the first inner ring spacer 45. For example, it is possible to omit the surface treatment layer 50 applied to the outer peripheral surface of the first outer ring spacer 41 that is liquid-tight sealed to the housing 2 by the O-ring 51, or the inner peripheral surface of the first inner ring spacer 45 that is liquid-tight sealed to the rotating shaft 3 by the O-ring 53.

[0030] The second inner ring spacer 15 fitted onto the rotating shaft 3 has an L-shaped cross section with a flange portion 16 protruding radially outward from the rear end of the outer peripheral surface. Thus, the flange portion 16 of the second inner ring spacer 15 covers the annular space between the inner ring and outer ring of the rolling bearing 21 in the first row from the axial front of the four rolling bearings 21 exposed to the liquid atmosphere, and can prevent liquid from entering the interior of the bearing.

[0031] As described above, according to the spindle unit 1 of the first embodiment, the surfaces of the first outer ring spacer 41 and the first inner ring spacer 45, which are disposed axially forward of the rolling bearing 21 and are exposed to a liquid atmosphere, are coated with the surface treatment layer 50 having water- and oil-repellent properties. As shown in Fig. 3, water droplets 65 that come into contact with the front end face (front axial end face) 45a of the first inner ring spacer 45 splash liquids such as grinding fluid radially outward due to centrifugal force, thereby improving waterproofing. Furthermore, the lotus effect of the surface having the minute irregularities and the surface treatment layer 50 breaks down water into droplets, which makes it difficult for the water droplets 65 to penetrate into the radial gap between the first outer ring spacer 41 and the first inner ring spacer 45.

[0032] Furthermore, the water- and oil-repellent effects improve the dischargeability of liquid that is thrown axially forward of the rolling bearing 21 by the centrifugal force of the first inner ring spacer 45 from the discharge port 33 of the outer ring holder 31. In addition, the water- and oil-repellent effects also improve the dischargeability of moisture that passes through the radial gap between the first outer ring spacer 41 and the first inner ring spacer 45 from the discharge port 14 and lubricant discharge port 35 of the second outer ring spacer 13.

[0033] Furthermore, according to the spindle unit 1 of the first embodiment, grease reservoir recesses 42, 46 are provided on the inner peripheral surface 41c of the first outer ring spacer 41 and the outer peripheral surface 45c of the first inner ring spacer 45, respectively, and are filled with grease 60. Thus, as the first inner ring spacer 45 rotates, only the grease 60 at the contact portions is removed between the grease reservoir recesses 42, 46, forming minute gaps. Therefore, the bank (bank) formed by the grease 60 makes it difficult for water droplets 65 that have entered the radial gap between the first outer ring spacer 41 and the first inner ring spacer 45 to penetrate inside. Furthermore, if the filled grease 60 is water-repellent, the waterproof effect is further enhanced.

[0034] Therefore, according to the spindle device 1 of the first embodiment, it is possible to prevent liquid from entering from the outside and improve waterproofing, thereby preventing a large amount of liquid splashed on the front surface of the spindle from entering the inside of the rolling bearing 21, thereby preventing problems such as poor lubrication of the bearing or seizure.

[0035] 4 is an enlarged cross-sectional view of a main portion of a front bearing device 20A in a spindle unit 1 according to a second embodiment of the present invention. Note that the front bearing device 20A according to this second embodiment has the same basic configuration as the front bearing device 20 of the first embodiment, and therefore the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0036] As shown in Figure 4, the front bearing device 20A according to the second embodiment comprises a first outer ring spacer 41 that is arranged axially forward (to the left in Figure 4) of the rolling bearing 21 that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing 21 axially relative to the housing 2, a second outer ring spacer 13 that is interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41, and an outer ring holder 31.

[0037] The front bearing device 20A also includes a first inner ring spacer 45 that is arranged radially inward of the first outer ring spacer 41 and positions the inner ring of the rolling bearing 21 axially relative to the rotating shaft 3, and a second inner ring spacer 15A that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45.

[0038] A surface treatment layer 50 (shown by cross-hatching in FIG. 4) with water- and oil-repellent properties is applied to the surfaces of the first outer ring spacer 41 and the first inner ring spacer 45. Therefore, water droplets 65 that come into contact with the front end surface 45a of the first inner ring spacer 45 cause liquids such as grinding fluid to fly outward in the radial direction due to centrifugal force, thereby improving waterproofing.

[0039] Furthermore, the second inner ring spacer 15A fitted onto the rotating shaft 3 is formed with an L-shaped cross section, with a flange portion 16 protruding radially outward from the rear end of the outer peripheral surface, and a surface treatment layer 50 having water and oil repellency is also applied to the surface (inner peripheral surface) of the second inner ring spacer 15A. The flange portion 16 of the second inner ring spacer 15A, on which the surface treatment layer 50 is applied, covers the annular space between the inner ring and outer ring of the rolling bearing 21 in the first row from the axial front of the four rolling bearings 21 that are exposed to a liquid atmosphere, providing a multi-stage water and oil repellent effect and further preventing liquid from penetrating into the bearing.

[0040] Therefore, according to the spindle device 1 equipped with the front bearing device 20A according to the second embodiment, in addition to the same effects as those of the spindle device 1 according to the first embodiment, it is possible to further improve waterproofing.

[0041] 5 is an enlarged cross-sectional view of a main portion of a front bearing device 20B in a spindle unit 1 according to a third embodiment of the present invention. Note that the front bearing device 20B according to this third embodiment has the same basic configuration as the front bearing device 20 of the first embodiment, and therefore the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0042] As shown in Figure 5, the front bearing device 20B according to the third embodiment comprises a first outer ring spacer 41 that is arranged axially forward (to the left in Figure 5) of the rolling bearing 21 that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing 21 axially relative to the housing 2, a second outer ring spacer 13 that is interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41, and an outer ring holder 31.

[0043] The front bearing device 20B also includes a first inner ring spacer 45B that is arranged radially inward of the first outer ring spacer 41 and positions the inner ring of the rolling bearing 21 axially relative to the rotating shaft 3, and a second inner ring spacer 15 that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45B.

[0044] 5, when arranged axially forward of the rolling bearing 21, the inner peripheral surface 41c of the first outer ring spacer 41 and the outer peripheral surface 45c of the first inner ring spacer 45B, which are closely opposed to each other, have a cylindrical shape extending axially forward. Furthermore, the inner peripheral surface 41c of the non-rotating side first outer ring spacer 41 is provided with a grease reservoir recess 42 into which grease 60 is filled, but the outer peripheral surface 45c of the rotating side first inner ring spacer 45B is not provided with a grease reservoir recess 46.

[0045] The surfaces of the first outer ring spacer 41 and the first inner ring spacer 45B are treated with a surface treatment layer 50 (shown cross-hatched in FIG. 5) that has water- and oil-repellent properties. Therefore, water droplets 65 that come into contact with the front end surface 45a of the first inner ring spacer 45B cause the centrifugal force to splash liquid such as grinding fluid radially outward, thereby improving waterproofing.

[0046] Furthermore, as the first inner ring spacer 45B rotates, only the grease 60 at the contact area is expelled, forming a minute gap between the grease 60 filled in the grease reservoir recess 42 and the outer peripheral surface 45c of the first inner ring spacer 45B. Thus, the bank formed by the grease 60 makes it difficult for water droplets 65 that have entered the radial gap between the first outer ring spacer 41 and the first inner ring spacer 45B to enter the interior of the bearing.

[0047] Therefore, according to the spindle device 1 equipped with the front bearing device 20B of this third embodiment, even if the grease reservoir recess 42 is provided only on the inner surface 41 c of the first outer ring spacer 41, it is possible to obtain the same effects as those of the spindle device 1 of the first embodiment.

[0048] 6 is an enlarged cross-sectional view of a main portion of a front bearing device 20C in a spindle unit 1 according to a fourth embodiment of the present invention. Note that the front bearing device 20C according to the fourth embodiment has the same basic configuration as the front bearing device 20 of the first embodiment, and therefore the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0049] As shown in Figure 6, the front bearing device 20C according to the fourth embodiment comprises a first outer ring spacer 41C that is arranged axially forward (to the left in Figure 6) of the rolling bearing 21 that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing 21 axially relative to the housing 2, a second outer ring spacer 13 that is interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41C, and an outer ring holder 31.

[0050] Furthermore, the front bearing device 20C is equipped with a first inner ring spacer 45C that is arranged radially inward of the first outer ring spacer 41C and positions the inner ring of the rolling bearing 21 axially relative to the rotating shaft 3, and a second inner ring spacer 15 that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45C.

[0051] 6, when arranged axially forward of the rolling bearing 21, the inner peripheral surface 41c of the first outer ring spacer 41C and the outer peripheral surface 45c of the first inner ring spacer 45C, which are closely opposed to each other, have a tapered shape that widens in diameter toward the axial front. Furthermore, the inner peripheral surface 41c of the first outer ring spacer 41C and the outer peripheral surface 45c of the first inner ring spacer 45C are each provided with grease reservoir recesses 42, 46 that are filled with grease 60.

[0052] Furthermore, a surface treatment layer 50 (shown by cross-hatching in FIG. 6) with water- and oil-repellent properties is applied to the surfaces of the first outer ring spacer 41C and the first inner ring spacer 45C. As a result, water droplets 65 that come into contact with the front end face 45a of the first inner ring spacer 45C cause liquids such as grinding fluid to fly outward in the radial direction due to centrifugal force, thereby improving waterproofing.

[0053] As described above, in the spindle unit 1 equipped with the front bearing device 20C according to the fourth embodiment, the inner circumferential surface 41c of the first outer ring spacer 41C and the outer circumferential surface 45c of the first inner ring spacer 45C have a tapered shape that widens in diameter toward the axial front. Therefore, water droplets 65 that have entered the radial gap between the first outer ring spacer 41C and the first inner ring spacer 45C are discharged axially forward of the first outer ring spacer 41C along the tapered inner circumferential surface 41c and outer circumferential surface 45c by the centrifugal force of the first inner ring spacer 45C.

[0054] Therefore, according to the spindle device 1 equipped with the front bearing device 20C according to the fourth embodiment, in addition to the same effects as those of the spindle device 1 of the first embodiment, it is possible to further improve waterproofing.

[0055] 7 is an enlarged cross-sectional view of a main portion of a front bearing device 20D in a spindle unit 1 according to a fifth embodiment of the present invention. Note that the front bearing device 20D according to the fifth embodiment has the same basic configuration as the front bearing device 20 of the first embodiment, and therefore the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0056] As shown in Figure 7, the front bearing device 20D of this fifth embodiment comprises a first outer ring spacer 41D that is arranged axially forward (left side in Figure 7) of the rolling bearing 21 that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing 21 axially relative to the housing 2, a second outer ring spacer 13D that is interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41D, and an outer ring holder 31.

[0057] Furthermore, the front bearing device 20D is equipped with a first inner ring spacer 45D that is arranged radially inward of the first outer ring spacer 41D and positions the inner ring of the rolling bearing 21 axially relative to the rotating shaft 3, and a second inner ring spacer 15 that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45D.

[0058] 7, when arranged axially forward of the rolling bearing 21, the inner circumferential surface 41c of the first outer ring spacer 41D and the outer circumferential surface 45c of the first inner ring spacer 45D, which are closely opposed to each other, have a cylindrical shape extending axially forward. Furthermore, the inner circumferential surface 41c of the first outer ring spacer 41D and the outer circumferential surface 45c of the first inner ring spacer 45D are each provided with grease reservoir recesses 42, 46 each formed of a pair (plurality of) circumferential grooves arranged along the axial direction of the rotating shaft 3, and each is filled with grease 60.

[0059] Furthermore, the first outer ring spacer 41D is provided with a circumferential discharge groove 47 with a V-shaped cross section that is provided on the inner peripheral surface 41c between the pair of grease reservoir recesses 42, and a discharge hole 48 that connects the circumferential discharge groove 47 with the rear end face 41b of the first outer ring spacer 41D. Also, the cylindrical second outer ring spacer 13D that is fitted within the housing 2 is formed with a communication hole 17 that connects the discharge port 14 with the discharge hole 48 of the first outer ring spacer 41D.

[0060] The surfaces of the first outer ring spacer 41D and the first inner ring spacer 45D are treated with a surface treatment layer 50 (shown cross-hatched in FIG. 7) that has water- and oil-repellent properties. Therefore, water droplets 65 that come into contact with the front end face 45a of the first inner ring spacer 45D cause the centrifugal force to splash liquid such as grinding fluid radially outward, thereby improving waterproofing.

[0061] As described above, in the spindle unit 1 including the front bearing device 20D according to the fifth embodiment, the first outer ring spacer 41D is provided with the discharge circumferential groove 47 provided in the inner peripheral surface 41c and the discharge hole 48 communicating with the discharge circumferential groove 47. Furthermore, the second outer ring spacer 13D is provided with the communication hole 17 communicating with the discharge port 14. Thus, water droplets 65 that have entered the radial gap between the first outer ring spacer 41D and the first inner ring spacer 45D are discharged from the discharge circumferential groove 47, which expands the space, through the discharge hole 48 and the communication hole 17, to the discharge port 14. As a result, it is possible to make it difficult for water droplets 65 that have entered the radial gap between the first outer ring spacer 41D and the first inner ring spacer 45D to enter the rolling bearing 21 side.

[0062] Therefore, according to the spindle device 1 equipped with the front bearing device 20D according to the fifth embodiment, in addition to the same effects as those of the spindle device 1 according to the first embodiment, it is possible to further improve waterproofing.

[0063] 8 is an enlarged cross-sectional view of a main portion of a front bearing device 20E in a spindle unit 1 according to a sixth embodiment of the present invention. Note that the front bearing device 20E according to the sixth embodiment has the same basic configuration as the front bearing device 20 of the first embodiment, and therefore the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0064] As shown in Figure 8, the front bearing device 20E according to the sixth embodiment comprises a first outer ring spacer 41E that is arranged axially forward (to the left in Figure 8) of the rolling bearing 21 that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing 21 axially relative to the housing 2, a second outer ring spacer 13 that is interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41E, and an outer ring holder 31.

[0065] Furthermore, the front bearing device 20E is equipped with a first inner ring spacer 45E that is arranged radially inward of the first outer ring spacer 41E and positions the inner ring of the rolling bearing 21 axially relative to the rotating shaft 3, and a second inner ring spacer 15 that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45E.

[0066] 8, when arranged axially forward of the rolling bearing 21, the inner peripheral surface 41c of the first outer ring spacer 41E and the outer peripheral surface 45c of the first inner ring spacer 45E, which are closely opposed to each other, have a cylindrical shape extending axially forward. Furthermore, the inner peripheral surface 41c of the first outer ring spacer 41E and the outer peripheral surface 45c of the first inner ring spacer 45E are each provided with grease reservoir recesses 42, 46 each formed of three circumferential grooves arranged along the axial direction of the rotating shaft 3, and each is filled with grease 60.

[0067] A surface treatment layer 50 (shown by cross-hatching in FIG. 8) with water- and oil-repellent properties is applied to the surfaces of the first outer ring spacer 41E and the first inner ring spacer 45E. Therefore, water droplets 65 that come into contact with the front end face 45a of the first inner ring spacer 45E cause the centrifugal force to splash liquid such as grinding fluid radially outward, thereby improving waterproofing.

[0068] As described above, in the spindle unit 1 equipped with the front bearing device 20E according to the sixth embodiment, the inner peripheral surface 41 c of the first outer ring spacer 41E and the outer peripheral surface 45 c of the first inner ring spacer 45E are each provided with a plurality of grease reservoir recesses 42, 46 (three circumferential grooves in this embodiment), and each is filled with grease 60. Thus, as the first inner ring spacer 45E rotates, only the grease 60 at the contact portions is removed between the grease reservoir recesses 42, 46, forming minute gaps. Therefore, the plurality of banks (embankments) formed by the grease 60 make it difficult for water droplets 65 that have entered the radial gap between the first outer ring spacer 41E and the first inner ring spacer 45E to penetrate inside.

[0069] Therefore, according to the spindle device 1 equipped with the front bearing device 20E according to the sixth embodiment, in addition to the same effects as those of the spindle device 1 according to the first embodiment, it is possible to further improve waterproofing.

[0070] 9 is an enlarged cross-sectional view of a main portion of a front bearing device 20F in a spindle unit 1 according to a seventh embodiment of the present invention. Note that the front bearing device 20F according to the seventh embodiment has the same basic configuration as the front bearing device 20 of the first embodiment, and therefore the same or corresponding parts are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0071] As shown in Figure 9, the front bearing device 20F according to the seventh embodiment comprises a first outer ring spacer 41F that is arranged axially forward (to the left in Figure 9) of the rolling bearing 21 that is exposed to a liquid atmosphere and that positions the outer ring of the rolling bearing 21 axially relative to the housing 2F, a second outer ring spacer 13 that is interposed between the outer ring of the rolling bearing 21 and the first outer ring spacer 41F, and an outer ring holder 31.

[0072] Furthermore, the front bearing device 20F is equipped with a first inner ring spacer 45 that is arranged radially inward of the first outer ring spacer 41F and positions the inner ring of the rolling bearing 21 axially relative to the rotating shaft 3, and a second inner ring spacer 15 that is interposed between the inner ring of the rolling bearing 21 and the first inner ring spacer 45.

[0073] 9, when arranged axially forward of the rolling bearing 21, the inner peripheral surface 41c of the first outer ring spacer 41F and the outer peripheral surface 45c of the first inner ring spacer 45, which are closely opposed to each other, have a cylindrical shape extending axially forward. Furthermore, the inner peripheral surface 41c of the first outer ring spacer 41F and the outer peripheral surface 45c of the first inner ring spacer 45 are each provided with grease reservoir recesses 42, 46 that are filled with grease 60.

[0074] Furthermore, the first outer ring spacer 41F fitted into the housing 2F is formed with a grease supply port 43 that penetrates radially and communicates with the grease reservoir recess 42. When the first outer ring spacer 41F is fitted into the housing 2F, it is assembled so that the grease supply port 43 communicates with the lubricant supply port 37 provided vertically above the housing 2F.

[0075] A surface treatment layer 50 (shown by cross-hatching in FIG. 9) with water- and oil-repellent properties is applied to the surfaces of the first outer ring spacer 41F and the first inner ring spacer 45. Therefore, water droplets 65 that come into contact with the front end surface 45a of the first inner ring spacer 45 cause liquids such as grinding fluid to fly outward in the radial direction due to centrifugal force, thereby improving waterproofing.

[0076] As described above, in the spindle unit 1 equipped with the front bearing device 20F according to the seventh embodiment, the first outer ring spacer 41F has the grease supply port 43 that penetrates radially and communicates with the grease reservoir recess 42, allowing additional grease 60 to be supplied to the grease reservoir recess 42. Thus, as the first inner ring spacer 45 rotates, only the grease 60 at the contact portions is removed between the grease 60 filled in the grease reservoir recesses 42, 46, creating a continuous, minute gap. Therefore, the bank (bank) formed by the grease 60 makes it difficult for water droplets 65 that have entered the radial gap between the first outer ring spacer 41F and the first inner ring spacer 45 to enter the interior stably over a long period of time.

[0077] Therefore, according to the spindle device 1 equipped with the front bearing device 20F according to the seventh embodiment, the same effects as those of the spindle device 1 of the first embodiment can be stably obtained over a long period of time.

[0078] The present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. Furthermore, the material, shape, size, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present invention.

[0079] Here, the features of the embodiment of the spindle device according to the present invention described above are briefly summarized and listed below in [1] to [7]. [1] A housing (2), a rolling bearing (21) that rotatably supports a rotating shaft (3) relative to the housing (2), a first outer ring spacer (41, 41C, 41D, 41E, 41F) that is arranged in front of the rolling bearing (21) that is exposed to a liquid atmosphere and positions an outer ring of the rolling bearing (21) relative to the housing (2) in the axial direction, and a first inner ring spacer (45, 45B, 45C, 45D, 45E) that is arranged radially inward of the first outer ring spacer (41, 41C, 41D, 41E, 41F) and positions an inner ring of the rolling bearing (21) relative to the rotating shaft (3) in the axial direction, a grease reservoir recess (42, 46) provided on at least one of an inner peripheral surface (41c) of the first outer ring spacer (41, 41C, 41D, 41E, 41F) and an outer peripheral surface (45c) of the first inner ring spacer (45, 45B, 45C, 45D, 45E), which are closely opposed to each other; a surface treatment layer (50) having water and oil repellency applied to each surface of the first outer ring spacer (41, 41C, 41D, 41E, 41F) and the first inner ring spacer (45, 45B, 45C, 45D, 45E); and grease (60) filled in the grease reservoir recess (42, 46).

[0080] According to the configuration [1], water droplets (65) contacting the front end surface (45a) of the first inner ring spacer (45, 45B, 45C, 45D, 45E) splash liquids such as grinding fluid radially outward due to centrifugal force, thereby improving waterproofing. Furthermore, the lotus effect of the micro-irregular surface breaks down water into droplets, making it difficult for water droplets (65) to penetrate into the radial gap between the first outer ring spacer (41, 41C, 41D, 41E, 41F) and the first inner ring spacer (45, 45B, 45C, 45D, 45E). Furthermore, the rotation of the first inner ring spacer (45, 45B, 45C, 45D, 45E) removes only the grease (60) from the contacting portions, forming minute gaps between the grease reservoir recesses (42, 46). Therefore, the embankment (bank) formed by the grease (60) makes it difficult for water droplets (65) that have entered the radial gap between the first outer ring spacer (41, 41C, 41D, 41E, 41F) and the first inner ring spacer (45, 45B, 45C, 45D, 45E) to penetrate inside.

[0081] [2] The spindle device (1) described in the above [1], wherein an inner peripheral surface (41 c) of the first outer ring spacer (41C) and an outer peripheral surface (45 c) of the first inner ring spacer (45C) have a tapered shape that increases in diameter axially forward.

[0082] According to the configuration [2] above, water droplets (65) that have entered the radial gap between the first outer ring spacer (41C) and the first inner ring spacer (45C) are discharged axially forward of the first outer ring spacer (41C) along the tapered inner peripheral surface (41c) and outer peripheral surface (45c) by the centrifugal force of the first inner ring spacer (45C).

[0083] [3] The spindle device (1) described in the above [1], wherein the grease reservoir recesses (42, 46) are configured by a plurality of circumferential grooves arranged along the axial direction of the rotating shaft (3).

[0084] According to the configuration [3] above, between the grease (60) filled in the grease reservoir recesses (42, 46) formed by the plurality of circumferential grooves, only the grease (60) at the contact portions is removed by the rotation of the first inner ring spacer (45E), forming minute gaps. Therefore, the plurality of banks (embankments) formed by the grease (60) make it difficult for water droplets (65) that have entered the radial gap between the first outer ring spacer (41E) and the first inner ring spacer (45E) to penetrate inside.

[0085] [4] The spindle device (1) according to the above item [3], further comprising: a discharge circumferential groove (47) provided on an inner peripheral surface (41 c) of the first outer ring spacer (41D); and a discharge hole (48) communicating between the discharge circumferential groove (47) and a rear end face (41 b) of the first outer ring spacer (41D).

[0086] According to the configuration [4] above, water droplets (65) that have entered the radial gap between the first outer ring spacer (41D) and the first inner ring spacer (45D) are discharged from the discharge circumferential groove (47) where the space is widened, through the discharge holes (48) and the communication holes (17). As a result, it is possible to make it difficult for the water droplets (65) that have entered the radial gap between the first outer ring spacer (41D) and the first inner ring spacer (45D) to enter the rolling bearing (21).

[0087] [5] A spindle device (1) according to the above item [1], comprising: a second outer ring spacer (13) having a discharge port (14) penetrating in the radial direction and interposed between the outer ring of the rolling bearing (21) and the first outer ring spacer (41); a second inner ring spacer (15A) having a flange portion (16) protruding radially inward from a rear end of the outer peripheral surface and interposed between the inner ring of the rolling bearing (21) and the first inner ring spacer (45); and a surface treatment layer (50) having water and oil repellency applied to the surface of the second inner ring spacer (15A).

[0088] According to the configuration [5] above, the flange portion (16) of the second inner ring spacer (15A) to which the surface treatment layer (50) is applied covers the annular space between the inner ring and the outer ring of the rolling bearing (21) that is exposed to a liquid atmosphere, and a multi-stage water- and oil-repellent effect is obtained, thereby making it possible to further suppress the intrusion of liquid into the inside of the bearing.

[0089] [6] The spindle device (1) according to the above-mentioned [1], wherein the grease reservoir recess (42) is provided only on the inner peripheral surface (41c) of the first outer ring spacer (41).

[0090] According to the configuration [6] above, a minute gap is formed between the grease (60) filled in the grease reservoir recess (42) and the outer peripheral surface (45c) of the first inner ring spacer (45B) by the rotation of the first inner ring spacer (45B), with only the grease (60) at the contact portion being expelled. Therefore, the bank (embankment) formed by the grease (60) makes it difficult for water droplets (65) that have entered the radial gap between the first outer ring spacer (41) and the first inner ring spacer (45B) to enter the inside of the bearing.

[0091] [7] The spindle device (1) according to the above-mentioned [1], wherein the first outer ring spacer (41F) has a grease supply port (43) that is radially penetrated and communicates with the grease reservoir recess (42), and additionally supplies grease (60) to the grease reservoir recess (42).

[0092] According to the configuration [7] above, the grease (60) can be additionally supplied to the grease reservoir recess (42), and minute gaps are continuously formed between the grease (60) filled in the grease reservoir recesses (42, 46) by the rotation of the first inner ring spacer (45), with only the grease (60) at the contacting portions being removed. Therefore, the bank (embankment) formed by the grease (60) makes it difficult for water droplets (65) that have entered the radial gap between the first outer ring spacer (41F) and the first inner ring spacer (45) to enter the interior stably for a long period of time.

[0093] This application is based on a Japanese patent application (Patent Application No. 2024-089011) filed on May 31, 2024, the contents of which are incorporated herein by reference.

[0094] According to the spindle device of the present invention, even when a large amount of liquid is sprayed onto the bearing, as in the case of a spindle device of a machine tool, it is possible to sufficiently prevent liquid from penetrating into the bearing, thereby preventing liquid from penetrating from the outside and improving waterproofing.

[0095] REFERENCE SIGNS LIST 1 spindle device 2 housing 3 rotating shaft 21 rolling bearing 41 first outer ring spacer 42 grease reservoir recess 45 first inner ring spacer 46 grease reservoir recess 50 surface treatment layer 60 grease

Claims

1. A spindle device comprising: a housing; a rolling bearing that rotatably supports a rotating shaft relative to the housing; a first outer ring spacer that is arranged in front of the rolling bearing exposed to a liquid atmosphere and positions the outer ring of the rolling bearing in the axial direction relative to the housing; a first inner ring spacer that is arranged radially inward of the first outer ring spacer and positions the inner ring of the rolling bearing in the axial direction relative to the rotating shaft; a grease reservoir recess provided on at least one of the inner peripheral surface of the first outer ring spacer and the outer peripheral surface of the first inner ring spacer that are closely opposed to each other; a surface treatment layer that has water and oil repellent properties and is applied to the surfaces of the first outer ring spacer and the first inner ring spacer; and grease filled in the grease reservoir recess.

2. A spindle unit as set forth in claim 1, wherein the inner peripheral surface of the first outer ring spacer and the outer peripheral surface of the first inner ring spacer are tapered so that their diameters increase axially forward.

3. The spindle device according to claim 1, wherein the grease reservoir recess is constituted by a plurality of circumferential grooves arranged along the axial direction of the rotating shaft.

4. A spindle device according to claim 3, comprising: a circumferential discharge groove provided on the inner peripheral surface of the first outer ring spacer; and a discharge hole communicating between the circumferential discharge groove and the rear end face of the first outer ring spacer.

5. A spindle device as set forth in claim 1, comprising: a second outer ring spacer having a discharge port penetrating radially and interposed between the outer ring of said rolling bearing and said first outer ring spacer; a second inner ring spacer having a flange portion protruding radially inward from the rear end of its outer peripheral surface and interposed between the inner ring of said rolling bearing and said first inner ring spacer; and a surface treatment layer having water and oil repellent properties applied to the surface of said second inner ring spacer.

6. The spindle unit according to claim 1, wherein the grease reservoir recess is provided only on the inner peripheral surface of the first outer ring spacer.

7. A spindle unit according to claim 1, wherein the first outer ring spacer has a grease supply port that is radially penetrated and communicates with the grease reservoir recess, and supplies additional grease to the grease reservoir recess.

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